A water craft, such as a surf-craft, particularly one on which a person stands, kneels or sits, when traversing water or riding a wave, generally has at least one fin in an underside of the craft, generally near the tail end of the craft. Such fins have a number of functions, including: enabling the craft to travel in a desired direction; facilitating the turning of the craft; preventing the craft from slipping sideways; and providing greater control over the movement of the craft, such as when riding a wave.
The following discussion is directed mainly to surf-craft, such as surfboards, but it is to be understood that the discussion applies equally to other water craft (and surf craft) which are adapted to include fins, such as sail boards, paddle boards, kite surf boards, rescue boards, surf skis, kayaks, and the like.
Some surf craft have the fins integrally formed on the surf craft and, for many years, this was the standard means for incorporating fins into such surfcraft. In the last twenty years or so, it has become more common for surfcraft to incorporate a removable fin or, more commonly, fin systems which include a number of removable fins. Such fin systems have numerous benefits, including enabling the fins to be removed for transportation and travelling, allowing damaged fins to be easily replaced and enabling fins of different shapes or styles to be selectively used. Such fin systems typically include at least one fin plug embedded into the underside of the surfcraft. This fin plug generally has at least one cavity adapted to receive a base portion (or a base element) of a surfcraft fin. The surfcraft fin is attached to the surfcraft by securing the base portion (or base element) of the fin into the cavity (or cavities) of the fin plug. There are numerous known fin systems which adopt this general arrangement.
One such known fin system is described in U.S. Pat. No. 5,464,359 in the name of Fin Control Systems Pty Ltd. This system includes fins having 2 projecting base elements (or tabs) and, for each fin, two fin plugs installed in the underside of the surfcraft. Each of the fin plugs has a cavity for receiving one of the base elements. Each fin plug also includes means for securing the base element into the cavity.
An alternative fin system is described in PCT/AU2008/001132, also in the name of Fin Control Systems Pty Ltd. This system also includes fins having 2 projecting base elements. However, these base elements are attachable to a single fin plug, having two cavities for receiving the two corresponding base elements.
Other known fin systems comprise a single fin plug, with a single cavity, for each fin. Typically, such a fin system has quite a large fin plug with an elongated fin cavity for receiving the base element of the fin. The fin plug of such systems also typically includes an upper flat portion having an opening from which the fin cavity extends inwardly and a flange section extending laterally about the opening. This flange section has a particular width. Extending downwardly from an underside of the flat upper portion is a body portion which surrounds the fin cavity. The shape of such a fin plug generally requires two cavities to be routed into the underside of the surfcraft in a two-step process. Firstly, a relatively wide, shallow cavity needs to be formed, the dimensions of which substantially correspond to the shape of the flange section. The depth of this first cavity will substantially correspond with the width of the flange section. Secondly, a narrow, deeper cavity needs to be formed in the first mentioned cavity, which is adapted to receive the body portion of the fin plug. As most surfcraft are designed to accommodate three fins, having to adopt this two-step process for forming each fin plug cavity in the surfcraft substantially slows down the installation process.
Another problem with known fin plugs is that the bond formed between the fin plug and the resinous material with which the fin plug is typically secured within a surfboard blank can be, or can become, flawed, particularly as a result of pressure placed upon the surfcraft fin (which, in use, is connected to the fin plug). The means by which a fin plug is secured within a surfcraft is typically by means of a harden-able liquid resinous material between external surfaces of the fin plug and the wall(s) of the cavity into which the fin plug is inserted.
In the fin system described in U.S. Pat. No. 5,464,359, each of the fin plugs has a top surface (being the surface on which the opening to the cavity is located) and following installation in the surfcraft, this top surface is exposed, being flush with the surface of the underside of the surfcraft.
In the fin system described in PCT patent application number PCT/AU2008/001132 published as WO 2009/021267 A1, each fin plug has a top surface (again being the surface on which the opening to each cavity is located). Following installation in the surfcraft, this top surface is not exposed but, rather, sits under a fiberglass layer. This fiberglass layer above the fin plug top surface is generally continuous with the fiberglass layer of the underside of the surfcraft. The fiberglass layer which sits over the top surface of the fin plug enhances the secure fixation of the fin plug to the surfcraft.
A further problem with most known fin plugs (such as those disclosed in U.S. Pat. No. 5,464,359) is that, when installed in a surfcraft, they are surrounded by the relatively low density foam of which the surfcraft is formed. Such foam may not generally provide sufficient strength to support the loads placed upon the fin plug, due to forces applied to the attached fin, without some deformation, weakening or crushing of the surrounding foam over time. Such deformation or weakening of the foam may cause the fin plug to sink into the foam or to shift out of alignment, with consequential reduction in performance of the attached fin. This can also cause the fiberglass skin, in the vicinity of the fin plug, to crack or shatter. Also, when the fin plug sinks into the foam body, it can cause the top surface of the fin plug to separate from the adjoining fiberglass layer.
Surfcraft fins can be subject to very substantial forces (especially lateral forces) when the surfcraft is undergoing a turn or upon impact with some other object and these forces are then transferred to the corresponding fin plugs to which the fins are attached. These forces can place very substantial strains on the connections (formed of hardened resinous material) between the fin plug and the surfcraft. In turn, these connections can be weakened and, in some cases, the hardened resinous material can crack). These strains upon the abovementioned connections are generally in inverse proportion to the total area of the external surfaces of the fin plug. Accordingly, the smaller this area, the greater will be the strain placed upon the relevant connection.
The present invention is directed towards ameliorating at least some of the above described problems associated with prior art fin plugs and, consequently, the methods of installing these. In particular, one object of the present invention is directed towards providing a fin plug assembly which is adapted to form a stronger bond with the resinous material with which it is secured to a surfcraft.
Any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates, at the priority date of this application.